1. Field of the Invention
The present invention relates to a single-stage backlight inverter for controlling driving of a cold cathode fluorescent lamp (CCFL) for a thin film transistor-liquid crystal display (TFT-LCD) panel, and more particularly to a single-stage backlight inverter and a method for driving the same, wherein switching signals to power switches for driving of a CCFL are phase-shifted to realize zero-voltage switching capable of adjusting the ratio of enable times of the power switches, thereby making it possible to reduce stresses on the power switches, readily control driving of the lamp and provide a switching control circuit in the form of an integrated circuit (IC) to simplify the configuration thereof.
2. Description of the Related Art
CCFLs for TFT-LCD panels are generally operated at low current, resulting in advantages such as low power consumption, low heat, high brightness and long life. In this connection, the CCFLs have recently been used in various display devices such as a backlight unit of a computer monitor, for example, a TFT-LCD, and a display panel of a printer. A high alternating current (AC) voltage of 1 to 2 kV is required to light such a CCFL, and an inverter is utilized to provide such a high AC voltage.
The inverter can be generally classified into two types, a single type (or a single-stage type) where one transformer is driven by one driver and a double type (or a two-stage type) where two transformers are driven in tandem by one driver.
FIG. 1 is a block diagram showing the configuration of a conventional backlight inverter.
The conventional backlight inverter shown in FIG. 1 is a two-stage backlight inverter and comprises a switching device 11 for converting a direct current (DC) voltage of about 5 to 30V into a square-wave voltage in response to a pulse width modulation (PWM) signal, a rectifier 12 for rectifying an output voltage from the switching device 11 by half wave, a transformer driver 13 for performing a self-oscillating function to convert an output voltage from the rectifier 12 into an AC voltage, a transformer device 14 for boosting an output AC voltage from the transformer driver 13 to a voltage level of about 1 to 2 kV necessary to a lamp operation, a lamp 15, such as a CCFL, connected to the transformer device 14 such that it is turned on/off in response to an output voltage from the transformer device 14, a feedback voltage detector 16 for detecting a voltage corresponding to current flowing through the lamp 15, and a dimming controller 17 for generating the PWM signal based on the voltage detected by the feedback voltage detector 16 and providing it to the switching device 11 to adjust a duty cycle of the square-wave voltage. The transformer driver 13 can be of any drive type based on a given circuit configuration.
With the above configuration, the conventional two-stage backlight inverter is adapted to drive the CCFL directly through the self-oscillating circuit to generate the transformer driving AC voltage.
However, the above-mentioned conventional two-stage backlight inverter is disadvantageous in that complex circuits, such as the self-oscillating circuit, a buck converter, etc., are required to apply an AC voltage to the transformer device so as to drive the CCFL, resulting in an increase in application costs of such circuits. Further, an associated control circuit is so complex that it is subject to a limitation in size reduction. This limitation causes difficulty in building it in one IC.